Exclusion of older adults from ongoing clinical trials about type 2 diabetes mellitus

Objective: To assess the extent of exclusion of older individuals from ongoing clinical trials regarding type 2 diabetes mellitus.

Design: Cohort study.

Setting: World Health Organization Clinical Trials Registry Platform.

Participants: Using the Participation of the Elderly in Clinical Trials methodology, data from ongoing clinical trials on type 2 diabetes mellitus were extracted from the platform on July 31, 2011.

Measurements: Proportion of trials excluding individuals using an arbitrary upper age limit or other exclusion criteria that might indirectly cause limited recruitment of older individuals. Exclusion criteria were classified as justified or poorly justified.

Results: Of 440 trials investigating treatments for type 2 diabetes mellitus, 289 (65.7%) excluded individuals using an arbitrary upper age limit. Such exclusion was significantly more common in trials with calculated sample sizes of less than 100 subjects (73.6% vs 59.5%; P = .002). Exclusion for comorbidity was present in 338 trials (76.8%); this exclusion was poorly justified in 236 trials (53.6%). Exclusion for polypharmacy (29.5% of trials), cognitive impairment (18.4%), short life expectancy (8.9%), and other poorly justified exclusion criteria that could limit the inclusion of older individuals was also present. Only six trials (1.4%) were designed specifically to study older adults.

Conclusion: Despite the recommendations of international regulatory agencies, exclusion of older individuals from ongoing trials regarding type 2 diabetes mellitus is frequent--higher than reported for other age-related diseases. This exclusion limits the value of the evidence that clinicians use when treating old, frail, complex patients with diabetes mellitus.